In recent years, increasingly sophisticated telematics systems have been developed to detect an emergency condition or activation, and in response, initiate a call to a call center. Systems have been developed for monitoring fixed customer premises locations or personnel at specific site as well as for vehicle applications. For motor vehicle applications, for example, an on-board system monitors one or more sensors to determine when a crash has occurred. Upon detecting a crash condition, the on-board system activates a cellular transceiver to initiate a cellular telephone call to a call center of the telematics service provider (TSP). Upon connection to the call center, the system may communicate certain data, such as location determined by global positioning satellite (GPS) processing, identification data and crash related data. After the data transmission, the call is converted to a voice call in which a TSP representative at the call center can attempt voice communication with an occupant of the vehicle. The TSP also offers mechanisms for the representative to contact emergency service personnel in the area, to respond appropriately to the incident.
With telematics communications of the type outlined above, whether for fixed location or vehicle applications, the ability to complete the emergency call to the TSP call center is of vital importance. The purpose of the telematics system is defeated if the call does not go through. A number of strategies have been developed to provide backup communication capabilities in the event that a primary communication network resource fails or is otherwise unavailable. For fixed location applications, for example, the primary resource typically is a local telephone line of the public switched telephone network (PSTN); and the backup is the cellular network. If the landline call is unsuccessful, the telematics unit automatically initiates a call to the TSP center using a cellular transceiver.
For mobile applications in vehicles, the primary communication resource is a cellular transceiver. However, more than one carrier often provides mobile service even in one geographic region. So, for mobile applications, the telematics unit may attempt a first cellular telephone call via the wireless network of one carrier/service provider; and if that call fails, then the unit will attempt a second similar cellular telephone call via the wireless network of a second different carrier/service provider using a preferred roaming list (PRL) scan algorithm. Another approach is to initiate a data session as a backup method of communications in the event the initial voice call fails; although selection of the carrier for the data session apparently has been limited to a primary wireless service provider for the location, as indicated on the PRL embedded in the communication device. It has also been suggested that the vehicular telematics unit may repeat its attempts on one carrier's cellular network, until the emergency call gets through to the TSP center.
These back-up strategies for telematics calls are not always adequate, particularly in the context of wireless communications, as they do not adequately cover enough of the reasonably anticipated failure scenarios. Previous methods for making an emergency call from a wireless device would make provisions only for wireless network failures. For example, repeated calls to a particular number through one carrier's network will experience the same communication problem unless and until the problem is cleared, whether the problem is due to a failure of the carrier's wireless facility or due to a failure of the landline network used to carry the call from the wireless domain to the TSP call center. Repeated wireless calls will repeatedly fail until the wireless network becomes accessible and/or the relevant landline communication is possible. In the context of an emergency, such as a vehicle crash, the delay in completing the notification could be disastrous to the victims.
The cause of communication problems experienced by cellular calls may be due to problems in the cellular network or problems in the landline communications between the cellular network and the TSP call center. Switching to an alternate wireless carrier network for the secondary call may avoid some cellular network issues but may not provide a path around a problem with a landline connection somewhere between the cellular carriers' networks at the crash site and the TSP call center location.
Switching to a data communication session via the wireless network of the carrier providing service for the voice call also may not address all problems. If there is a problem with the primary service provider's wireless network or its landline interface, that problem may impact data communications as well as voice communications. Depending on the location, a backup carrier on the PRL may not be available and/or the alternate carrier identified by PRL may be experiencing similar difficulties impacting both voice calls and data communications.